1. Field of the Invention
The present invention relates to a semiconductor device and an IC card having a non-volatile memory, more specifically to a technology for reliably initializing data in the non-volatile memory.
2. Description of the Related Art
A non-volatile memory, which is capable of retaining data without any power supply thereto, is often installed in LSI. Any necessary initial data is stored in the non-volatile memory when the non-volatile memory is installed in LSI, and the LSI provided with the non-volatile memory in which such necessary data is stored is shipped. Examples of the initial data include product management information used when the LSI is manufactured, various information used when the quality of a product is judged and various data such as model-specific information, as recited in Japanese Patent Document (Japanese Patent Laid-Open Publication No. 2000-259602). Such data is used in order to facilitate maintenance service when the product is found defective after the shipment.
In the LSI installed in the IC card, a transportation key is used in order to prevent any illegal use resulting from theft of the LSI and the IC card during the transportation (for example, see Japanese Patent Document (Japanese Patent Laid-Open Publication No. 2004-102635)). Information of the transportation key is stored in the non-volatile memory as initial data when the LSI is manufactured, and then, the LSI is shipped. In addition to the above-mentioned data, other initial data such as configuration information for setting functions of the LSI is also stored in the non-volatile memory by a manufacturer of the LSI.
There are a wide variety of non-volatile memories, including a ferroelectric memory, EEPROM, a fuse memory and a mask ROM, and each of these memories has advantages and disadvantages. For example, the ferroelectric memory is advantageous in its remarkable access speed and rewritability; however, is unfavorably inferior to the other non-volatile memories in its anti-stress properties (heat-resistant stress property and anti-stress property. Further, the fuse memory, for example, is superior in its anti-stress properties and data retaining performance; however, is disadvantageously rewritable only once.
The LSI may undergo some kind of stress in any of manufacturing steps before the LSI is made into a final product. For example, when the LSI is mounted on a substrate, a thermal stress of approximately 250° C. is applied to the LSI in a reflow step wherein the LSI package is soldered to the substrate. However, in the case where the ferroelectric memory is used as the non-volatile memory, the initial data may be destroyed due to the thermal stress during a manufacturing step. On the other hand, in the case of the fuse memory and the EEPROM whose anti-stress properties are high, such basic performance as the access speed and rewritability fail to satisfy demanded specification.